Organic Photorefractive Materials

Photorefractive inorganic materials have been studied for some time as holographic media, but advances in photorefractive organic materials are relatively... 

Wurthner F, WOTtmann R, Meerholz K (2002) ChnunophOTe design for photorefractive organic materials. Chemphyschem 3 17—31... 

For typical NLO-phores the (ju, ) 6a term is much larger than the p,gl3 term. The molar polarizabilities (113) and (114) were recently used to derive a molecular figure of merit (FOM) for NLO-phores for organic photorefractive (PR) materials with low glass-transition temperature (Wortmann et al., 1996). Rational design of NLO-phores based on this FOM led to organic PR-materials with unprecedented performance (Wtirthner et al., 1997). 

More recently the promising range of applications for photorefractive materials has motivated the rapid development of amorphous, organic materials with a strong photorefractive response [5]. Here the chemical composition of the materials may be varied with relative ease and the opportunity to compare materials from different sources should exist. The various processes necessary for photorefraction may be obtained by a single material, or many different molecular species may be mixed in a composite to provide the range of properties needed. These amorphous materials do not have a well-defined mobility for the photogenerated holes that... 

Photorefractivity in an organic material was first reported in 1990 [36] by the ETH Zurich group in an organic single crystal. The same year a group at Eastman Kodak developed a multifunctional polymer that showed photoconductivity and... 

Within a relatively short time, many polymeric materials were developed that do exhibit the photorefractive effects. These materials consist of polymers with charge transport agents and photosensitizing dyes. The quantity of change in a material s refractive index that is altered by alterations in an applied electric field is expressed as the electrooptic coefficient r. Lithium niobate has an r value of 30 pm / volt. Several polymers are already known that possess coefficients (at 1.3 pm) greater than 30 pmW and the aim now is to develop materials with r values of 50 pm / volt or even higher. It is also known that the photorefractive effect can also be observed in many organic materials. 

O. Ostroverkhova and W. E. Moerner, Organic photorefractives mechanisms, materials, and applications. Chem Rev 104 (2004), 3267-314. 

Since the discovery of the photorefractive effect in LiNbOj crystals, early investigations dealt exclusively with — incidentally, expensive — inorganic single crystals (e.g., LiNbOj, BaTiOj) and semiconductors (e.g., GaAs). Difficulties in the processing of these materials into the desired (thin film) forms have hampered practical applications. The first observation of photorefractivity in an organic material in 1990 caused attention to spread to photorefractive polymers because they can be easily modified and processed into a variety of thin film configurations as required by the application. ... 

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